Hot melt adhesives are widely used in industry for various applications. Typical applications include product assembly, packaging such as case, carton or tray forming, and in glue sticks. Hot melt adhesives in use today are generally based on ethylene vinyl acetate copolymers (EVA) and low molecular weight polyethylene homopolymers (LMPE). Desirable properties in a hot melt adhesive include: (a) suitability for high temperature end use; (b) low temperature flexibility; (c) low viscosity; and (d) thermal stability, to name but a few. Conventional hot melt adhesives, however, typically lack one or more such properties. LMPE-based hot melt formulations can have good elevated temperature end use characteristics, but are undesirably brittle at low temperatures. EVA copolymers are prone to char, skin or gel when exposed to elevated temperatures in the presence of air. In addition, EVA-based adhesives generally have poor elevated temperature performance.
Ethylene acrylate copolymers available commercially today, such as ethylene methyl acrylate or ethylene n-butyl acrylate copolymers, can be formulated to give hot melt adhesives that have good thermal stability and low temperature flexibility, but these formulations still lack in elevated temperature performance. High temperature performance can be improved by addition of high melting point waxes, but such waxes significantly increase the cost of the adhesive. Thus, it would be desirable to have adhesive formulations with good elevated and low temperature performance, good adhesion to a variety of substrates, and excellent thermal stability, without the need for large amounts of expensive, high melting point waxes.